Comparing Angular 6 Subjects and BehaviorSubject

Recently, I developed an application where I utilized the behavior subject for data transfer between all components. I am curious to know if this is considered a best practice when working with observables.

import { BehaviorSubject } from 'rxjs';

const subject = new BehaviorSubject(123);

// Two new subscribers will initially receive the value => output: 123, 123
subject.subscribe(console.log);
subject.subscribe(console.log);

// Two subscribers will now receive the new value when it changes => output: 456, 456
subject.next(456);

// A new subscriber will receive the latest value (456) => output: 456
subject.subscribe(console.log);

Answer №1

Topic: When it comes to observables, a Subject is like a live update feature that notifies subscribers of new values without keeping track of old ones. Once a value is emitted by a Subject and a subscriber joins later, that initial value will not be received. It's similar to a continuous feed of updates where only the latest values are captured.

UniqueSubject: In contrast, a BehaviorSubject functions similarly to a regular Subject but with an added twist - it stores the last emitted value. If a subscription is made after a value has been emitted by a BehaviorSubject, the subscriber will receive the most recent value. Additionally, the last value emitted by a BehaviorSubject can be accessed using .value on the BehaviorSubject itself.

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